1. Field of the Invention
The present invention relates to a simplified type screen printing machine for printing an object to be pressed mounted on a print base by using a framed stencil sheet assembly, particularly to a simplified type screen printing machine for easily exerting tension to a framed stencil sheet assembly and providing distinct picture.
2. Description of the Related Art
Screen printing method is suitable for a print face, the surface of which is smooth and which is difficult to absorb ink. According to the screen printing method, as is well known, there is used a screen 53 laminated together with a thermoplastic resin film 52 and a porous support 51 as shown by FIGS. 12(a), 12(b), 12(c) and 12(d). The screen 53 is perforated and four peripheries thereof are fixed to a plate frame 54 with tension.
As shown by FIG. 12(a), the screen 53 is opposed to a print base member 56 on which an object to be printed 55 is mounted to be spaced apart therefrom by a predetermined interval and is fixed thereto by predetermined tension. Further, when as shown by FIG. 12(b), screen printing ink 57 is placed on the screen 53 and while pressing a surface of the screen 53 (porous support 52) by a squeegee 58, a rear face of the screen 53 (thermoplastic resin film 51) is brought into contact with the object to be printed 55 and squeegeed, as shown by FIG. 12(c), the ink 57 passes through opening portions of the plate where the thermoplastic resin film 51 is not present from the porous support 52 and is extruded onto the object to be printed 55. When the squeegee operation is finished, as shown by FIG. 12(d), the screen 53 is recovered to an original state by tension of the screen 53.
However, according to the above-described printing, the screen 53 needs to fix with tension by being floated up from the print face of the object to be printed 55 by the predetermined interval. Further, the squeegee 58 is partially depressed onto the screen 53 fixed with tension and therefore, adjustment of force exerted on the squeegee 58 is difficult and differs by operators. Therefore, considerable skill is needed for uniformly squeegeeing the surface of the screen 53 by pertinent depressing force. Further, some degree of rigidity is needed for the plate frame 54 and therefore, it is difficult to use a frame member having weak rigidity such as a frame member made of paper.
The present invention has been carried out in order to remove the above-described drawback and it is an object thereof to exert predetermined tension to a framed stencil sheet assembly over an entire face of an object to be pressed by pressing the stencil sheet assembly to a base member to be brought into contact with the object to be pressed and fixing the framed stencil sheet assembly with tension.
Further, it is other object thereof to make a image forming material pass through a framed stencil sheet assembly by image forming means in a state of exerting predetermined tension to the framed stencil sheet assembly to thereby form image having a uniform distinctness over an entire face of an object to be pressed constituting an object to be pressed even when pressure applied on the framed stencil sheet assembly by the image forming means is not uniform.
It is still other object thereof to form perforations which have a uniform distinctness by uniformly irradiating light over an entire face of the draft constituting an object to be pressed by providing attachably and detachably a light irradiating apparatus for irradiating light to perforate a framed stencil sheet.
Further, it is other object thereof to make the uniform tension of a framed stencil sheet assembly by relievably fixing pressing means to a base member in a state in which the framed stencil sheet assembly is fixed with tension to an object to be pressed on a base member. Particularly, it is the object of the present invention to provide further distinct perforations in perforating operation and to provide further distinct image in printing operation.
It is still other object thereof to carry out screen printing and plane press type printing by a single printing machine by interchangeably constituting pressing means and pressing means with transparent plate provided with a transparent plate at an opening portion.
According to a first aspect of the present invention, there is provided a simplified type screen printing machine comprising a base member on which an object to be pressed is mounted, a framed stencil sheet assembly at least constituted by stencil sheet comprising a porous support and a resin film laminated to the support and a frame member laminated with the stencil sheet, and pressing means attachably and detachably attached with the framed stencil sheet assembly for pressing the framed stencil sheet assembly to the base member to be brought into contact with the object to be pressed to fix the framed stencil sheet assembly.
Further, according to a second aspect of the present invention, there is provided the simplified type screen printing machine according to the first aspect wherein an object to be printed is mounted as the object to be pressed, further comprising image forming means for making an image forming material pass through the framed stencil sheet assembly which is fixed with tension.
Further, according to a third aspect of the present invention, there is provided the simplified type screen printing machine according to the first aspect wherein an original for perforating the framed stencil sheet assembly is mounted as the object to be pressed, further comprising a light irradiating apparatus attachably and detachably mounted to the pressing means for irradiating light to the stencil sheet of the framed stencil sheet assembly which is fixed with tension.
Further, according to a fourth aspect of the present invention, there is provided the simplified type screen printing machine according to any one of the first through the third aspects wherein the pressing means is provided with an opening portion openably and closably supported axially by the base member and attachably and detachably attached with the framed stencil sheet assembly.
Further, according to a fifth aspect of the present invention, there is provided the simplified type screen printing machine according to any one of the first through the third aspects wherein the pressing means is provided to the base member as a separate member and provided with an opening portion attachably and detachably attached with the framed stencil sheet assembly.
Further, according to a sixth aspect of the present invention, there is provided the simplified type screen printing machine according to anyone of the fourth or the fifth aspect, further comprising a print base comprising an elastic member for mounting the object to be pressed provided on an upper face of the base member, and wherein at least a portion of the print base is disposed at inside of the opening portion when the framed stencil sheet assembly is fixed to the object to be pressed on the base member by predetermined tension.
Further, according to a seventh aspect of the present invention, there is provided the simplified type screen printing machine according to anyone of the first through the sixth aspects, further comprising fixing means for relievably fixing the pressing means to the base member in a state in which the framed stencil sheet assembly is fixed to the object to be pressed on the base member tense by the predetermined tension.
Further, according to an eighth aspect of the present invention, there is provided the simplified type screen printing machine according to any one of the first through the seventh aspects wherein the pressing means can be interchanged with pressing means having a transparent plate provided with the transparent plate at the opening portion and wherein the stencil sheet assembly is further provided with an ink-unpermeable back sheet pasted at the frame member.
In perforating operation, firstly, the light irradiating apparatus is mounted to the opening portion of the pressing means. The pressing means is pressed to the base member, the framed stencil sheet assembly is brought into contact with an original and the framed stencil sheet assembly is fixed with tension. At this occasion, at least a portion of the print base provided at the base member is disposed at inside of the opening portion of the pressing means. Further, a pivotal end of the pressing means and the base member are brought into contact with each other, electricity is conducted to the light irradiating apparatus and light is irradiated to the stencil sheet of the framed stencil sheet assembly which has been fixed with tension. The stencil sheet is formed with desired perforated image in accordance with an original image.
In printing operation, the light irradiating apparatus is removed. The pressing means is pressed to the base member, the framed stencil sheet assembly which has been perforated is brought into contact with an object to be printed and the framed stencil sheet assembly is fixed with tension. At this occasion, at least a portion of the print base provided at the base member is disposed at inside of the opening portion of the pressing means. From this state, the image forming material is made to pass through the perforated stencil sheet by the image forming means. The image forming material which has passed therethrough reaches the object to be printed and desired image is formed.